Urinary N tau-methylhistamine during early and late allergen-induced bronchial-obstructive reactions.

Urinary N tau-methylhistamine, a unique histamine metabolite, was determined in 29 patients with bronchial asthma before and after inhalation of a control solution on 1 day and before and after allergen inhalation on another day. Twenty-eight patients had an early bronchial-obstructive reaction, defined by a decrease in FEV1 of 20% or more within 1 hr after allergen inhalation. A late bronchial-obstructive reaction, 3 to 8 hr after allergen inhalation, was found in 16 patients. The early bronchial-obstructive reaction was attended with a significantly increased N tau-methylhistamine excretion. The fall in FEV1 was correlated with the degree of bronchial hyperreactivity to histamine, but no significant correlation was found with the increase in urinary N tau-methylhistamine excretion. During the late reaction there was no significant difference in the change in N tau-methylhistamine excretion when the change was compared with that of the control day. These results suggest that a renewed degranulation of lung mast cells during the late bronchial-obstructive reaction is unlikely.